1. Field of the Invention
The invention is directed to a cutting insert, especially for use with metalworking operations, having a geometry making it suitable for mounting in different toolholder pockets. The invention is also directed to the combination of such an insert in a toolholder.
2. Description of the Prior Art
Cutting inserts are well-known, and a large percentage of them are of the throw-away design. Such inserts are detachably clamped on a holder and then are discarded when they become dull or chipped. Throw-away inserts are usually indexable and often reversible so that an insert can be provided with at least two cutting edges for selective presentation to the cutting position. The availability of two or more cutting edges on the insert makes it economical to use and is particularly important with respect to throw-away inserts because of the high cost of the materials from which the inserts are produced, especially when the material is, for example, a cemented carbide.
These inserts must be securely and accurately held in place within a toolholder during a cutting operation. This is especially true when the inserts are used with numerically controlled machines which depend for accuracy upon an accurately located and firmly supported insert. When the inserts are relatively large and have a substantial mounting area, it is possible to secure the insert both accurately and firmly within the pocket of a toolholder by providing the insert with a central hole and the toolholder with a pin-type clamping device.
For grooving, cutoff and threading operations, the cutting insert is frequently mounted in the toolholder pocket on its edge, and oftentimes the insert is not large enough to permit a hole in the insert for a pin-type clamp. Under these circumstances, it is necessary to use a top clamp to hold the insert in place. However, such an arrangement may not provide suitable support to the insert for lateral loads that may be applied to the insert during machining operations such as turning or profiling.
A prior art cutting insert and toolholder are shown in FIGS. 1-2. The cutting insert is generally indicated by the reference character 10. The insert 10 comprises an insert body 15 having a first end 20, a second end 25, a first side 30, a second side 35, and top and bottom walls 40 and 45, respectively. At the juncture of the first end 20 and the top wall 40, there is one cutting edge 50. At the juncture of the second end 25 and the bottom wall 45, there is a second cutting edge 55.
A toolholder 100 for use in combination with the insert 10 has a bar-like member 105 adapted for being clamped in a tool support of any suitable type. At one end of the member 105 there is an insert pocket 110 having a bottom wall 115, a side wall 120, and a back wall 125. An undercut 130 is provided at the juncture of the bottom wall 115 and back wall 125 to protect the cutting edges 50, 55 of the insert 10 which are disposed in that region in each clamped position of the insert 10. The bottom wall 115 and the back wall 125 of the insert pocket 110 are at right angles to the side wall 120 and converge with one another in the direction toward the back of the pocket 110. A first groove 60 and a second groove 65 of the insert 10 are adapted for engagement by a nose 135 on one end of a clamping member 140.
Clamping member 140 has a leg 145 adapted for being received in a recess 150 formed in the top of the toolholder 100. A clamp screw 155 extends through a hole in the clamping member 140 between the legs thereof and into a threaded hole 160 provided in the top wall of the toolholder 100.
When the insert 10 is placed in the pocket 110, the clamping member 140 is put in position and screw 155 is tightened so that the insert 10 is pressed firmly against the bottom wall 115 of the pocket 110 while simultaneously being drawn toward the side wall 120 and the back wall 125. The insert is thereby clamped in the pocket 110 in the toolholder 100 and is located by being forced against the side wall 120 and back wall 125 of the pocket 110. A more detailed description of this arrangement is in U.S. Pat. No. 3,754,309 entitled "cutting Insert and Clamping Arrangement Therefor," which patent is assigned to the assignee of the present invention and hereby incorporated by reference.
This configuration provides a stable arrangement for grooving and cutoff operations where the cutting edge is urged against the toolholder pocket in a direction perpendicular to the cutting edge. This arrangement is suitable to withstand a relatively large force F1 (FIG. 1) which may be applied to the cutting edge at the side of the cutting edge closest to the first side 30, forcing the insert against the side wall 120. This arrangement is also suitable for light threading operations in which the cutting edge is urged with a relatively low force F2 (FIG. 1) away from the insert pocket.
However, this arrangement may not be suitable for machining applications which apply a large cutting force F2. Such a force tends to overcome the diagonal retaining force applied by the clamping member 140 and displace the insert 10 along the bottom wall 115 of the insert pocket 110. As a result, while this arrangement is suitable for a large variety of applications, it is not suitable for applications which apply a large lateral load toward the open side of the insert pocket 110.
The arrangement illustrated in FIGS. 1-2 is currently widely used in industry, and an arrangement is desired which would be capable of withstanding not only forces applied in a direction perpendicular to the cutting edge toward the insert pocket but also to withstand forces applied away from the insert pocket. Furthermore, it is desirable to modify the aforementioned insert to provide lateral support but also to ensure such modifications would not affect the capability of that cutting insert 10 to be used in the toolholder 100 illustrated in FIG. 2.
An object of the invention is to firmly hold an insert in a pocket when the insert is positioned on edge in the pocket so the insert may withstand the lateral forces associated with turning and profiling operations as well as the vertical forces associated with grooving, threading and cutoff operations. Another object is to accurately locate an insert when it sits on edge in a pocket.
It is a further object to provide a cutting insert which may accommodate a toolholder having a pocket with a flat floor as well as to accommodate a toolholder having a pocket with an angled floor.